Mucosal epithelium is widely distributed over tissues in cornea, gastrointestinal tract and the like. Mucosal epithelium maintains the moisture at a tissue surface, and serves to protect the body homeostasis against change in the external environment. However, depending on various factors, the wetting characteristic of a tissue surface may decrease, resulting in diseases such as dry eye and gastrointestinal tract ulcer.
In recent years, as a branch of regenerative medicine, a therapy has gathered attention in which a cell sheet obtained by plane-culturing mucosal epithelial cells is transplanted in living tissues which have lost mucosal epithelium. For example, a sheet of human mucosal epithelial cells is already in use for cornea transplantation.
However, the manufacture of a cell sheet generally requires complicated culture processes, and is susceptible to cell conditions and culture environment. Accordingly, a technology for evaluating the quality of a manufactured cell sheet is demanded. In particular, for a sheet of mucosal epithelial cells, wetting characteristic serves as an important measure of whether the cell sheet is capable of covering affected tissues.
The wetting characteristic of an object may be evaluated, for example, by the contact angle between a liquid and a surface of the object (the contact angle method). In other words, the larger is the value of the contact angle, the lower is the wetting characteristic, and the smaller is the value of the contact angle, the higher is the wetting characteristic. In the contact angle method, a droplet may be formed on a surface of an object for which wetting characteristic is to be evaluated to measure the contact angle. Alternatively, in the contact angle method, a surface of an object for which wetting characteristic is to be evaluated may be immersed into a liquid with face-down, and air and the like may be supplied from below to allow the air to adhere on the surface. Then the contact angle may be measured.
The wetting characteristic of a planar object such as a sheet and a plate may also be evaluated based on the force required to pull the object out of a liquid after the object is suspended in the liquid (the Wilhelmy plate method).
Meanwhile, in the field of cell biology, fluorescence microscopy is used for detecting specific intracellular proteins (Nonpatent Literature 1).